15.04 Hyperparathyroidism

Primary hyperparathyroidism (high secretion of the parathyroid hormone from the parathyroid glands) is a common endocrine disorder, especially in postmenopausal women. It is usually caused by parathyroid adenoma (tumours) or spontaneous hyperplasia. When there are high levels of parathyroid hormone, there is increased resorption of calcium from bones, and increased absorption of calcium from the gastrointestinal tract and kidneys. With high plasma levels of calcium and high urine phosphate levels, there can be renal stones, and bone pain leading to lesions and fractures. Secondary hyperparathyroidism is associated with chronic renal insufficiency. Surgery removing part of the parathyroid gland is probably the main treatment for hyperparathyroidism.

Cinacalcet is the drug used to treat hyperparathyroidism. Cinacalcet increases the sensitivity of calcium-sensing receptors to calcium, which turns off the stimulus for parathyroid hormone secretion. In addition to turning off parathyroid hormone secretion, cinacalcet inhibits parathyroid cell proliferation and parathyroid hormone synthesis.